Enzymes 2

Question 1

What are the feature of an enzyme active site

Answer 1

Many sidechains pointing inwards
Formation of weak bonds to substrate - weak = not overly favorable still reacts
determinie the specific reaction occuring

Question 2

What is the energy transition as a substrate binds and is convered to product in an enzyme

Answer 2

Energy decreases as ES is formed then increases to transition state then falls lower to products

Question 3

What are the advantages of weak bonds in the active site

Answer 3

Many of them present
Only form in specific orientations to keep specific geometry
easy to break

Question 4

What are the types of bonds found in enzyme active sites

Answer 4

Ionic bonds / salt bridges: formed from ionisable side chais (glu, his, asp)
H-bonds: can form from the AA backbone using dipol interactions
Van der Waals interactions: Very weak close proximity bonds
covalent bonds: very rare as to strong for enzyme active sites

Question 5

What is the induced fit model of the enzyme active site
+ an example of this

Answer 5

Enduced model shows how the active site is dynamic, will move around the substrate when it is in place.
Can tell the differences between isomers asuming aymetry

Hexokinase two sections fold around glucose substrate whne it enters the active site undergoing conformational change

Question 6

What are the three ways enzymes can catalyse reactions

Answer 6

decrease stability of the substrate
increase stability of the transition state
provide an alternate pathway with lower G energy

1+ 2 achived through enzyme active site being favorable to transition state

Question 7

Why are transition state analoges used in drug reserch,
+ example

Answer 7

Transition state is favoured by lots of enzymes. Making a molecule which mimics this state will bind to the enzyme better than the substate, can be used to make enzyme inhibitor drugs.
hard as transition state itself cannot be isolated

example:
liptor = cholestrol inhibitor drug, lowers cholestrol levers

Question 8

What are 5 methods to reduce G used by enzymes

Answer 8

Preferential transition state: stabilises transition state
specific orientation + proximity: ensures the correct orientation for reaction and holds reactants close
acid base catalysts: Involes the transfer of protons
metal ions catalysts: Uses a lewis acid to be an electron aceptor, can increase nucleophalicity
covalent catalysts: Often rare, short lived interaction, must be broken to reset the active site

Question 9

What intermediate is formed during covalent catylisation

Answer 9

Short lived reactive intermediate
formed between nucleophlic sidechain of enzyme and elecrophile of substrate